334 THE JOURNAL OF GEOLOGY. 
this test by reducing series of measurements under each of the 
two postulates, and our conclusions are of the same tenor. 
Treating fourteen measurements, he found the results obtained 
under the postulate of rigidity fifteen times as discordant as the 
results under the postulate of isostasy; treating twenty-six 
measurements, I found the ratio as six to one. These measure- 
ments pertain to stations distributed among the plateaus that 
make up the continent, plateaus ranging in general attitude from 
100 feet to 8700 feet; and the comparison shows that these 
plateaus are approximately in isostatic equilibrium. 
G. K. GILBERT. 
